According to the graph, we can see that the white cans cool a little bit slower than black cans on the same conditions.
On the first ten minutes, we can see that the temperature of water in black cans decreased from 100°C to 50°C. and the temperature of water in white cans decreased from 100°C to 75°C.
To explain this, you need to know what is a dark and white color?
it's a color in which the total absorption of all wavelengths and none of these wavelengths will be reflected. But since light is a form of energy expression, we can conclude that the black color has no energy on it. on the opposite of the white color, which absorbs all wavelengths, so it has energy on it (which will turn into heat), and that's why it could keep the temperature better than the dark color (all is about energy).